START Protein Domain

The START domain of human MLN64.

Domain Binding and Function

Both the CSD and BA START domain families share a common topology consisting of a seven stranded core β sheet centered between a pair of α helices at the N-terminus and an α helix at the C-terminus. The C-terminal α helix is packed tightly against the sheet, consistent with a Helix-Grip type fold. A striking feature of the START domains is the long hydrophobic tunnel expanding throughout the length of the domain. By adopting a structure similar to an incomplete β barrel, the interior face of the β sheet forms the bottom and sides of this tunnel. The C-terminal helix forms the tunnel roof.